Bug 1314861: Add defineLazyGetter global to SDK loader modules. r=ochameau

MozReview-Commit-ID: L1NShFpnb2S

--HG--
extra : rebase_source : 8d4b132da64a3af03a120f45f160731295a8b086

addon-sdk/source/lib/toolkit/loader.js

@@ -41,7 +41,9 @@ XPCOMUtils.defineLazyServiceGetter(this, "zipCache",
                                    "@mozilla.org/libjar/zip-reader-cache;1",
                                    "nsIZipReaderCache");
 
-XPCOMUtils.defineLazyGetter(this, "XulApp", () => {
+const { defineLazyGetter } = XPCOMUtils;
+
+defineLazyGetter(this, "XulApp", () => {
   let xulappURI = module.uri.replace("toolkit/loader.js",
                                      "sdk/system/xul-app.jsm");
   return Cu.import(xulappURI, {});
@@ -476,6 +478,14 @@ const load = iced(function load(loader, module) {
       descriptors[name] = getOwnPropertyDescriptor(globals, name)
       descriptors[name].configurable = true;
     });
+    descriptors.lazyRequire = {
+      configurable: true,
+      value: lazyRequire.bind(sandbox),
+    };
+    descriptors.lazyRequireModule = {
+      configurable: true,
+      value: lazyRequireModule.bind(sandbox),
+    };
     Object.defineProperties(sandbox, descriptors);
   }
   else {
@@ -730,6 +740,56 @@ const resolveURI = iced(function resolveURI(id, mapping) {
 });
 Loader.resolveURI = resolveURI;
 
+/**
+ * Defines lazy getters on the given object, which lazily require the
+ * given module the first time they are accessed, and then resolve that
+ * module's exported properties.
+ *
+ * @param {object} obj
+ *        The target object on which to define the lazy getters.
+ * @param {string} moduleId
+ *        The ID of the module to require, as passed to require().
+ * @param {Array<string | object>} args
+ *        Any number of properties to import from the module. A string
+ *        will cause the property to be defined which resolves to the
+ *        same property in the module's exports. An object will define a
+ *        lazy getter for every value in the object which corresponds to
+ *        the given key in the module's exports, as in an ordinary
+ *        destructuring assignment.
+ */
+function lazyRequire(obj, moduleId, ...args) {
+  let module;
+  let getModule = () => {
+    if (!module)
+      module = this.require(moduleId);
+    return module;
+  };
+
+  for (let props of args) {
+    if (typeof props !== "object")
+      props = {[props]: props};
+
+    for (let [fromName, toName] of Object.entries(props))
+      defineLazyGetter(obj, toName, () => getModule()[fromName]);
+  }
+}
+
+/**
+ * Defines a lazy getter on the given object which causes a module to be
+ * lazily imported the first time it is accessed.
+ *
+ * @param {object} obj
+ *        The target object on which to define the lazy getter.
+ * @param {string} moduleId
+ *        The ID of the module to require, as passed to require().
+ * @param {string} [prop = moduleId]
+ *        The name of the lazy getter property to define.
+ */
+function lazyRequireModule(obj, moduleId, prop = moduleId) {
+  defineLazyGetter(obj, prop, () => this.require(moduleId));
+}
+
+
 // Creates version of `require` that will be exposed to the given `module`
 // in the context of the given `loader`. Each module gets own limited copy
 // of `require` that is allowed to load only a modules that are associated

devtools/shared/worker/loader.js

@@ -123,6 +123,79 @@ function createModule(id) {
   });
 }
 
+function defineLazyGetter(object, prop, getter) {
+  let redefine = (obj, value) => {
+    Object.defineProperty(obj, prop, {
+      configurable: true,
+      writable: true,
+      value,
+    });
+    return value;
+  };
+
+  Object.defineProperty(object, prop, {
+    configurable: true,
+    get() {
+      return redefine(this, getter.call(this));
+    },
+    set(value) {
+      redefine(this, value);
+    }
+  });
+}
+
+/**
+ * Defines lazy getters on the given object, which lazily require the
+ * given module the first time they are accessed, and then resolve that
+ * module's exported properties.
+ *
+ * @param {object} obj
+ *        The target object on which to define the lazy getters.
+ * @param {string} moduleId
+ *        The ID of the module to require, as passed to require().
+ * @param {Array<string | object>} args
+ *        Any number of properties to import from the module. A string
+ *        will cause the property to be defined which resolves to the
+ *        same property in the module's exports. An object will define a
+ *        lazy getter for every value in the object which corresponds to
+ *        the given key in the module's exports, as in an ordinary
+ *        destructuring assignment.
+ */
+function lazyRequire(obj, moduleId, ...args) {
+  let module;
+  let getModule = () => {
+    if (!module) {
+      module = this.require(moduleId);
+    }
+    return module;
+  };
+
+  for (let props of args) {
+    if (typeof props !== "object") {
+      props = {[props]: props};
+    }
+
+    for (let [fromName, toName] of Object.entries(props)) {
+      defineLazyGetter(obj, toName, () => getModule()[fromName]);
+    }
+  }
+}
+
+/**
+ * Defines a lazy getter on the given object which causes a module to be
+ * lazily imported the first time it is accessed.
+ *
+ * @param {object} obj
+ *        The target object on which to define the lazy getter.
+ * @param {string} moduleId
+ *        The ID of the module to require, as passed to require().
+ * @param {string} [prop = moduleId]
+ *        The name of the lazy getter property to define.
+ */
+function lazyRequireModule(obj, moduleId, prop = moduleId) {
+  defineLazyGetter(obj, prop, () => this.require(moduleId));
+}
+
 /**
  * Create a CommonJS loader with the following options:
  * - createSandbox:
@@ -491,6 +564,8 @@ this.worker = new WorkerDebuggerLoader({
     "rpc": rpc,
     "URL": URL,
     "setImmediate": setImmediate,
+    "lazyRequire": lazyRequire,
+    "lazyRequireModule": lazyRequireModule,
     "retrieveConsoleEvents": this.retrieveConsoleEvents,
     "setConsoleEventHandler": this.setConsoleEventHandler,
   },